In Fig. 1.2.1, the global hydrologic cycle is represented as a system. The dashed lines divide it into three subsyterns: the atmospheric water system containing the processes of precipitation, evaporation, interception, and transpiration; the surface water system containing the processes of overland flow, surface runoff, subsurface and groundwater outflow, and runoff to streams and the ocean; and the subsurface water system containing the processes of infiltration, groundwater recharge, subsurface flow and groundwater flow. Subsurface flow takes place in the soil near the land surface; groundwater flow occurs deeper in the soil or rock strata.